6,028 research outputs found
Expressed sequence tags from the oomycete fish pathogen Saprolegnia parasitica reveal putative virulence factors
Peer reviewedPublisher PD
The Variable-Atmosphere Wave Tank
A facility was constructed for the study of water-entry,
water-exit, and underwater trajectory behavior of
small momentum-propelled missiles for varied trajectory
launching angles, missile accelerations and velocities,
wave fields and conditions of cavitation. A unique feature
is the electromagnetic missile propulsion system.
The facility is made principally of non-magnetic and
electrically non-conducting materials to permit the determination of missile accelerating force from the reactive force on the launching coil
Fluid Free Surface Proximity Effect on a Sphere Vertically Accelerated from Rest
Theory is developed to estimate the effect of free
surface proximity on the initial added mass of a sphere
accelerated vertically upward from rest in an ideal fluid.
It is assumed that the acceleration regime is sufficiently
brief that inertial forces predominate and gravitational
effects may be neglected. Results of tests in water indicate
that while there are slight viscous and gravitational effects
over the acceleration regime, the agreement between theory
and experiment is good. It is concluded that over briefer
acceleration regimes these effects would decrease and the
agreement would improve
Ultrasonic Imaging Systems
The use of ultrasonic imaging systems for non-destructive evaluation is increasing, with particular interest being paid to research into real time and quasi-real time imaging systems. Photos are shown which were taken using an electronically scanned and focused real time ultrasonic imaging system. The system can be operated with longitudinal waves, shear waves, Rayleigh waves, and lamb waves in the 1.5 MHz to 3.5 MHz frequency range, and has been successfully used on composite materials (boron fiber epoxy on titanium) and on a number of metals (steel, aluminum, and titanium). This system has been operated in both transmission and reflection modes; examples of each are shown
Full capacitance matrix of coupled quantum dot arrays: static and dynamical effects
We numerically calculated the full capacitance matrices for both
one-dimensional (1D) and two-dimensional (2D) quantum-dot arrays. We found it
is necessary to use the full capacitance matrix in modeling coupled quantum dot
arrays due to weaker screening in these systems in comparison with arrays of
normal metal tunnel junctions. The static soliton potential distributions in
both 1D and 2D arrays are well approximated by the unscreened (1/r) coulomb
potential, instead of the exponential fall-off expected from the often used
nearest neighbor approximation. The Coulomb potential approximation also
provides a simple expression for the full inverse capacitance matrix of uniform
quantum dot arrays. In terms of dynamics, we compare the current-voltage (I-V)
characteristics of voltage biased 1D arrays using either the full capacitance
matrix or its nearest neighbor approximation. The I-V curves show clear
differences and the differences become more pronounced when larger arrays are
considered.Comment: 8 pages preprint format, 3 PostScript figure
Interactive effects of joint angle, contraction state and method on estimates of Achilles tendon moment arms
The muscle-tendon moment arm is an important input parameter for musculoskeletal models. Moment arms change as a function of joint angle and contraction state and depend on the method being employed. The overall purpose was to gain insights into the interactive effects of joint angle, contraction state and method on the Achilles tendon moment arm using the center of rotation (COR) and the tendon excursion method (TE). Moment arms were obtained at rest (TErest, CORrest) and during a maximum voluntary contraction (CORMVC) at four angles. We found strong correlations between TErest and CORMVC for all angles (0.72 ≤ r ≤ 0.93) with Achilles tendon moment arms using CORMVC being 33 - 36% greater than those obtained from TErest. The relationship between Achilles tendon moment arms and angle was similar across both methods and both levels of muscular contraction. Finally, Achilles tendon moment arms for CORrest were 1 – 8% greater than for CORMVC. [NB rendition of scientific symbols is approximate in this display; please check full text for precise rendition]
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